如何显示学生人数最少的部门的名称

Question

如何编写查询以显示学生人数最少的部门的名称。按部门名称升序排列结果

Answer 1

select d.department_name from 
(select dd.department_name, count(di.department_id) as id from student di
join department dd on di.department_id=dd.department_id group by dd.department_name) d,
(select min(count(*)) as new from student group by department_id) d2
where d.id=d2.new;

Answer 2

select d.department_name from Department d, Student s where 
d.department_id = s.department_id
group by d.department_name
having count(s.student_id)<=all
(select count(s.student_id) from Department d, Student s where 
d.department_id = s.department_id
group by d.department_name)
order by department_name;

试试这个。

Answer 3

select d.department_id, d.department_name 
from Department d
join Student s on d.department_id = s.department_id
group by d.department_id
having count(s.student_id) = (select min(count(s2.student_id))
                              from student s2 
                                    join department d2 
                                    on s2.department_id = d2.department_id 
                               group by d2.department_id) 
order by d.department_name

您必须连接 2 个表才能获得所需的信息。

您还必须按所选信息对他们进行分组，以便统计学生人数。

最后，您设置条件。需要一个子查询来检索最少学生数。

Answer 4

select department_name
  from Department
    join Student
     on Department.department_id=Student.department_id
       having count(*) in
        ( select min(count(*)) from Student group by department_id)
        group by Department.department_id,department_name
        order by department_name asc;